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Effects of crude protein intake from grass silage-only diets on the equine colon ecosystem after an abrupt feed change¹

S. Muhonen^*,2, M. Connysson^*, J. E. Lindberg^*, V. Julliand, J. Bertilsson^* and A. Jansson^*

^* Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, S-75007 Uppsala, Sweden; and Etablissement National d’Enseignement Supérieur Agronomique de Dijon (ENESAD), 21079 Dijon, France

² Corresponding author: Sara.Muhonen{at}huv.slu.se

The objective of this study was to investigate the effect of CP intake from 2 grass silage-only diets, differing in CP concentration, fed at similar DMI on the equine colon ecosystem after an abrupt feed change between the diets. Four adult right ventral colon-fistulated geldings were fed one silage-only diet high in CP (HP, 873 g of CP/d) and one diet providing recommended intakes (RP, 615 g of CP/d). An adaptation period of 15 d on either the HP or the RP diet was followed by 2 experimental periods when the diets were fed for 22 d each in a crossover design. Colon samples were taken before and at 4, 12, and 24 h, and at 7, 14, and 22 d after the feed change. During the first 24 h after the abrupt feed change, the concentrations of total anaerobic bacteria and lactobacilli were greater on the HP than the RP diet (7.1 vs. 6.7 log₁₀ cfu/mL, P = 0.021, 6.0 vs. 5.5 log₁₀ cfu/mL, P = 0.021, respectively). During the first 24 h post feed change, VFA concentrations did not differ between the diets. From 7 to 22 d, total VFA concentrations were greater on the HP diet than on the RP diet (51.8 vs. 45.1 mmol/L, P = 0.034), and colon pH was lower on the HP diet than on the RP diet (6.9 vs. 7.2, P = 0.035). After an adaptation period of 22 d, N, ammonia, and urea concentrations and osmolality of the colon fluid did not differ between diets. Fecal pH and colon and fecal DM were unchanged throughout the experiment. The results suggest that, in horses fed at the maintenance level of energy intake, a feed change between silages with different CP content may alter the colon bacterial counts within the first 24 h. Moreover, during the subsequent 3 wk, pH decreased slightly and VFA concentrations increased, but no other major alterations occurred in the composition and activities of the colon ecosystem or fecal DM.

Key Words: colon microflora • equine • nitrogen • pH • protein intake • silage

This article has been cited by other articles:

				S. Muhonen, V. Julliand, J. E. Lindberg, J. Bertilsson, and A. Jansson Effects on the equine colon ecosystem of grass silage and haylage diets after an abrupt change from hay J Anim Sci, July 1, 2009; 87(7): 2291 - 2298. [Abstract] [Full Text] [PDF]